The Author(s) 2018. This article is published with open access at www.chitkara.edu.in/publications.

ABSTRACT

The existing passive radon monitors, their relative calibration facilities together with the past intercomparison exercises have been mission-oriented towards radon measurements in dwellings. These monitors have been successfully applied throughout the world for radon measurements in homes, characterized by temperatures in the range from 20 to 25°C and a relative humidity less than 50 R.H. A multitude of different problems may arise when these passive monitors are used in environment other than homes, such as in soil and in workplaces, where large humidity up to 100 RH and temperatures anywhere from 0°C to 40°C may be encountered. Under severe environmental conditions, different measurement errors may occur which have remained concealed to date. These errors may be caused by a drastic change of both the radon diffusivity through the and for the monitor housing respectively. permeation membranes or the radon absorption by the plastics, used for the track detector. For the compliance to the assessment of the occupational exposures, it is necessary to eliminate all the possible sources of errors, which may be conducive to litigation. Another important shortcoming of the existing passive monitors is the difficult to turn them on/off daily, as required for radon measurements in workplaces. Finally, most of the problems, listed above, can be solved by the exploitation of a new generation of passive monitors, known as Rn film-badges. These monitors are similar and often identical to neutron film-badges, which have proved to be very successful throughout the world for the personnel neutron dosimetry. In particular, the present paper will describe the unique characteristics of these radon film badges, such as compactness, fast time response, any desired response sensitivity, simplicity in turning them on and off, etc.

INTRODUCTION

A new generation of radon monitors has been recently developed, based on radon sorption in solids [1]. Since there is already a multitude of different well-established radon monitors [2], the development of new detectors is justified only if they make it possible to carry out measurements, which are difficult, if not impossible, to carry out with existing technologies. As already proved, these newlydeveloped monitors present unique characteristics for the correct measurements of radon in soil and in water with concentrations from a few kBq/m3 to tens of thousands kBq/ m3 [3]. In particular, these monitors, known as the radon film badges, show promise for the assessment of the radon exposures in workplaces. These occupational exposures to radon can’t be simply obtained by the passive monitors, typically used for indoor measurements, especially because of their limited response sensitivity, their long responsetime, and the difficulty to turn them on and off. To this end, it is interesting to report what John Harley [4] had to say about using the same approach of the indoor radon-monitoring for the assessment of occupational exposure to radon: “If a health physicist were to recommend monitoring the exposure of workers by placing a single detector in the middle of a nuclear facility, he would be removed in a straightjacket. When we do the same thing in a house, everyone agrees. So keep in mind that, even with the best of instruments, we may not be monitoring the right thing in the right place”. Any attempt, made in the past, to use the existing passive monitors in environment other than dwellings has encountered many difficulties. For example, since 1981, it was demonstrated how poor were the characteristics of the cup-type diffusive chamber for the assessment of the occupational exposure in mines [5]. The response of this monitor was affected by the atmospheric pressure and/or altitude [6] and by the chamber design and geometry. Finally, Frank and Benton [5] proved that most of these shortcomings could be overcome by keeping the maximum dimensions of the chamber less than 2.5 cm and by using a conductive detector holder. In yet another important example, the passive Rnmonitors, developed for indoor measurements, proved to be drastically affected by the humidity and the presence of thoron, when used for in-soil-radon measurements. Eventually these problems have been solved by using a permeation-type of sampler [7,8]. Among all the existing passive monitors, the permeation samplers are considered to be the least affected by ambient conditions, including humidity, air current, temperature, the presence of thoron, etc. [9, 2]. However, these conclusions are true for radon monitoring in homes, but they have proved to be totally wrong for radon monitoring in workplaces, which may be characterized by a wide range of temperatures (0-40°C) and humidity up to 100% RH. [10,3]. Unfortunately, the widespread calibration facilities and the many international inter-comparisons, carried out since the 1980s [11] have been all mission-oriented toward home-environmental conditions with temperatures between 20-25°C and low relative humidity (namely 30% RH). For these reasons, inter-comparison exercises run under field conditions (humidity up to 100% RH and temperatures from 0°C to 40°C), are very valuable to identify the shortcomings of existing Rn-monitors, when used in environments other than homes, such as in workplaces, etc.

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